To straighten a distracted spine, in particular in the case of scoliosis, it is well known to use vertebral osteosynthesis equipment including anchoring members for anchoring to the vertebrate (pedicle screws and/or lamina hooks), connecting bars, and connectors for connecting said bars to said anchoring members.
This type of equipment assumes that pedicles that are slightly or not at all deteriorated exist for anchoring screws, or that there are sufficient spaces at the laminas to engage the hooks behind said laminas. This type of equipment is therefore not suitable when the pedicles of the vertebrae are deteriorated or the spaces are insufficient at the vertebral laminas, as is the case when the spine is greatly distracted and/or when the vertebrae are significantly pivoted and/or deformed.
This type of equipment is also not suitable when it is necessary to perform a fairly significant “derotation” of one or more vertebrae, i.e. to pivot said vertebra(e) around themselves on the cervico-caudal axis so as to resituate them in normal anatomical positions.
For such indications of significantly distracted spines, significantly pivoted and/or deformed vertebrae, or significant “derotations,” it is known from document EP 2 279 707 A1 to use equipment including, aside from connecting bars and connectors, flexible ligaments that can be engaged around the laminas of the vertebrae to be treated. These ligaments are connected, by the connectors, to a connecting bar which itself is connected to the healthy vertebrae situated at the ends of the vertebral segment be treated, and are used to perform traction on the series of vertebrae to be straightened. The straightening of this series of vertebrae is done progressively, by performing successive straightening operations on the vertebrae in intermediate straightening positions and by going from one vertebra to the next successively.
Such ligaments are in particular made up of plaits of polyester fibers, with a circular or flat section.
The existing equipment including these ligaments appears not to be fully satisfactory. In fact, the strength of the connection of the ligaments to the connectors appears uncertain over time. Furthermore, the force that must be exerted on a ligament to perform a derotation of a vertebra is significant, which makes that derotation operation relatively complex, difficult and long. Furthermore, the instruments used to act on the connectors when traction is exerted are not optimal.